In a co-pending application for U.S. Letters Patent, Ser. No. 654,426 filed Feb. 2, 1976 by I. E. Dolgen and assigned to the same assignee as the present invention there is described and claimed an apparatus for transporting small amounts of material from a supply to another location a short distance away. In that apparatus a ladle type sample transport conveys small discrete analytical specimens, contained in pellets or capsules, from a supply magazine to the combustion chamber of a combustion elemental analysis instrument in which the sample material is burned and the combustion products analyzed to determine quantitatively the presence of a particular element, e.g., carbon, hydrogen, nitrogen.
The present invention relates to sample transport apparatus of the type described in the aforementioned copending application and, in particular, to a subsystem thereof for transferring the sample pellets to the ladle and discharging combustion residue from the ladle while maintaining the interior of the total transport apparatus sealed against entry of the ambient atmosphere. For convenience and clarity of understanding, the transport system of this invention is hereinafter described with particular reference to its adaptation for use with such a combustion elemental analytical instrument but it will be understood that it would also be useful in other applications.
In order to provide accurate analysis with the aforesaid types of analytical instruments discrete samples are customarily burned in a controlled atmosphere, e.g., in pure oxygen, at a particular pressure; accordingly, it is necessary to provide for purging the combustion volume between successive burnings and to seal this volume against entry of the ambient atmosphere. Obviously, it is necessary to provide access to the chamber in order to introduce samples and remove the ash residue after combustion and analysis has been accomplished. It is also highly desirable that the introduction of samples and removal of combustion residue be effected in an automatic sequence.
At present, in one known type of combustion analysis instrument, material to be analyzed is loaded into a platinum capsule which is then placed in a ladle-type boat. The end of a transfer tube is opened and the loaded boat is inserted. The tube is closed and a purge gas is circulated through the system to eliminate contaminants entering when the tube is opened; then the loaded boat is advanced through the transfer tube to the combustion chamber by means of a magnet moved manually along the outside of the tube. After combustion, the boat with the capsule containing ash is magnetically withdrawn from the combustion chamber and back to the loading end of the tube which is opened for removal of combustion residue and introduction of a new sample capsule. Due to the foregoing manual loading and feeding and the need to purge the system for each load, the procedure is cumbersome, tedious and very time-consuming when a series of analyses is to be performed.
Automatic loading systems have been proposed in which some sort of mechanical transport mechanism, adapted for automated sequential operation, is employed but in previously known mechanical systems the mechanisms for carrying capsules from a magazine to the combustion chamber and then to a residue receiving and holding tube or cavity are rather complex and take up a disproportionate amount of space. Moreover, the automation of sample loading represents only a partial solution to the problem of expediting analysis where extensive purging is required between each sample.
It is, therefore, a general object of the present invention to provide an automatic sample transport apparatus which overcomes or mitigates the shortcomings of comparable prior art devices as discussed above. A more specific object is the provision of automatic sampling apparatus for analytical instruments that is compact, mechanically simple, and reduces or eliminates the need for purging to maintain a controlled atmosphere.